The subject matter of the present invention relates to perforating guns for perforating oil well boreholes, and more particularly, to various phasing arrangements of charges in the perforating gun, such as an arrangement for producing an asymmetrical pattern of recesses in the perforating gun carrier and subsequently the same pattern of holes in an oil well borehole casing.
Perforating guns are used to perforate a formation surrounding an oil well borehole, or perhaps a casing which lines the borehole formation. Some perforating guns are used in deviated boreholes, such as horizontal boreholes. These perforating guns contain charges that are usually directed in a substantially downward direction. However, two very important parameters must be carefully considered when designing a perforating gun for use in deviated boreholes: (1) the density (in shots per foot) of the charges in the gun, and (2) the relative distribution (phasing) of the charges in the gun. The charge density and distribution parameters are important, since these parameters determine the flow rate of the formation fluids from the formation, and the strength of the casing after the charges in the gun have detonated. Unless the density of the charges in the perforating gun is carefully selected, taking into consideration the phasing and relative distribution of the charges per foot, the flow rate of the fluids originating from the formation may be too low to properly justify, from a cost effectiveness point of view, the use of the deviated well, and the strength of the casing, after charge detonation, may be too weak to justify continued use of the deviated well. Therefore, when designing a perforating gun, for use in deviated boreholes, in order to optimize flow rate of formation fluids originating from the formation and simultaneously maintain maximum casing strength, great care must be taken with respect to selection of the proper density of the charges in the gun, per foot, the degree or nature of the phasing of the charges and the distribution of the charges in the gun.